published_or_final_version / Physics / Doctoral / Doctor of Philosophy

There is a continued interest in the properties of arsenic thiolate compounds for both industrial and biological uses. Recent discoveries in the medicinal properties of such compounds have resulted in a sustained need for the synthesis of new dithiarsolane compounds for research as anti-leukemic compounds. Close analogues of the 2-halo arsenic dithiolates, namely those with an arsenic-carbon bond instead of an arsenic-halide bond, have recently been shown to have some efficacy towards leukemia cells. Based on the hydrolytic character and the active role of glutathione with arsenic in vivo, the compounds reported here may also have such activity. Arsenic compounds have demonstrated biological activity in the literature, thus the hypothesis of this thesis is cyclized arsenic thiolates can be synthesized with the appropriate characteristics as to be potentially useful medicinal agents as well as provide new structural and reaction information. A series of arsenic and antimony di- and trithiolates has been synthesized and characterized. Those compounds include 2-chloro-1,3,2-dithiarsolane, 2-bromo- 1,3,2-dithiarsolane, 2-iodo-1,3,2-dithiarsolane, 2-chloro-1,3,2-dithiarsenane, 2-bromo- 1,3,2-dithiarsenane, 2-iodo-1,3,2-dithiarsenane, 3-chloro-4H,7H-5,6-benz-1,3,2- dithiarsepine, 2-chloro-benzo-1,3,2-dithiarsole, 1,2-bis-dithiarsolan-2-ylmercapto-ethane, tris-(pentafluorophenylthio)-arsen, bis(2-(1,3,2-benzodithiarsol-2ylsulfanyl)- benzenesulfide), 2-chloro-benzo-1,3,2-dithiastibole, and bis(2-(1,3,2-benzodithistibol)- 1,2-benzenedithiol. Elucidation of the pH characteristics of arsenic dithiolates within the human toxicity reaction pathway is an area of interest. It has been shown that the aqueous arsenic dithiolate stability depends on the size of the ring. 2-Chloro-1,3,2-dithiarsolane has been shown to be somewhat stable at both low and high pH as well as neutral pH. 1,2-bis- Dithiarsolan-2-ylmercapto-ethane is completely stable in a neutral aqueous solution. Glutathione does not permanently bind to arsenic even in overwhelming excess. In particular, these fully characterized compounds determine how reactive the AsS and AsCl linkages are under environmental and biological conditions, and provide a source of new reagents to examine in medical applications. Future applications may include the incorporation of the reported compounds in filtration and remediation technologies with further modification.

This thesis contains two main parts: the first part focusses on an electron diffraction study on unsupported antimony (Sb) clusters, while in the second part the design and development of a time-of-flight mass spectrometer (TOFMS) is discussed. Electron diffraction is an ideal tool to study the structure of clusters entrained in a beam. The main advantage of this technique is the ability to study the clusters in situ and in an interaction-free environment. It is therefore not necessary to remove the particles from the vacuum system which would lead to oxidation. Since the particles do not have to be deposited on a sample for further investigation, there is also no substrate which could influence the cluster structure. An additional advantage is the short exposure to the electron beam, thereby minimising the likelihood of damaging the particles. Sb clusters were produced using an inert-gas aggregation source. To control the cluster properties the source temperature, pressure and type of cooling gas can be adjusted. In the range of source parameters tested, Sb clusters with three different structures were observed: a crystalline structure corresponding to the rhombohedral structure of bulk Sb, an amorphous structure equivalent to the structure of amorphous Sb thin films, and a structure with the same diffraction signature as Sb4 (Sb evaporates mainly as Sb4). This last structure was found to belong to large particles consisting of randomly oriented Sb4 units. In order to study the size distributions and morphologies of the Sb clusters, the clusters were deposited onto substrates and studied under an electron microscope. The crystalline particles showed a wide variety of strongly faceted shapes. Depending on source conditions, the average cluster diameters ranged from 15 to 130 nm. There was a considerable disagreement between these values and the size estimates from the diffraction results with the latter being smaller by an order of magnitude. This might be due to the existence of domains inside the clusters. The amorphous particles were all found to be spherical with mean sizes between 27 and 45 nm. The Sb4 particles showed a liquid-like morphology and tended to coalesce easily. Their sizes ranged from 18 to 35 nm. To obtain an independent method for determining the cluster size, a TOFMS was designed and developed in collaboration with Dr Bernhard Kaiser. However, the TOFMS failed to detect a cluster signal in the original set-up which is most likely due to a defective ioniser and underestimated cluster energies. Further tests were performed in a new vacuum system and mass spectra for palladium clusters were successfully recorded.

No description available.

Leishmanioses são um complexo de doenças infecciosas causadas por protozoários intramacrofágicos do gênero Leishmania, fatal se não tratadas adequadamente. Os antimoniais pentavalentes são os medicamentos de primeira escolha para o tratamento, apesar de sua toxicidade e seu mecanismo de ação pouco esclarecido. Uma terapia mais eficaz pode ser conseguida pelo direcionamento de fármacos antileishmania para os locais de infecção. Os lipossomas são vesículas lipídicas que promovem melhora na eficácia e na ação de fármacos na célula alvo. Os lipossomas são capturados preferencialmente pelas células do sistema mononuclear fagocitário (SMF). O objetivo deste estudo foi desenvolver uma formulação de antimoniato de meglumina lipossomal, constituído por fosfatidilserina e estudar sua farmacocinética em animais sadios para esclarecer seu metabolismo e distribuição. As análises quantitativas de antimônio em lipossomas demonstram que Análise por Ativação Neutrônica foi a técnica mais sensível com cerca de 100 % de precisão. Todas as formulações de lipossomas apresentaram um tamanho de diâmetro médio de 150 nm. A determinação da CE50 em macrófagos infectados mostrou que as formulações de antimoniato de meglumina encapsulado em lipossomas foram entre 10 - 63 vezes mais eficazes do que a fármaco livre, indicando maior índice de seletividade. Por microscopia de fluorescência, foi verificada uma maior internalização de lipossomas fluorescentes em macrófagos infectados durante um curto tempo de incubação em comparação com macrófagos não infectados. A biodistribuição do antimoniato de meglumina irradiado encapsulado em lipossomas contendo fosfatidilserina mostrou que a formulação lipossomal promoveu um direcionamento seletivo do antimônio para tecidos do SMF, além do que manteve as doses elevadas nos órgãos por um período prolongado. Em conclusão, estes dados sugerem que o antimoniato de meglumina encapsulado em lipossomas apresentou maior eficácia do que a fármaco não lipossomal contra a infecção por Leishmania. O desenvolvimento de formulações lipossomais pode ser uma nova alternativa para a quimioterapia de doenças infecciosas, especialmente Leishmanioses, já que são usados como sistemas carreadores para entrega sustentada e direcionada de fármacos ao local da infecção. / Leishmaniases are a complex of parasitic diseases caused by intramacrophage protozoa of the genus Leishmania, and is fatal if left untreated. Pentavalent antimonials, though toxic and their mechanism of action being unclear, remain the first-line drugs for treatment. Effective therapy could be achieved by delivering antileishmanial drugs to these sites of infection. Liposomes are phospholipid vesicles that promote improvement in the efficacy and action of drugs in target cell. Liposomes are taken up by the cells of mononuclear phagocytic system (MPS). The purpose of this study was to develop a preparation of meglumine antimoniate encapsulated in liposomes of phosphatidylserine and to study its pharmacokinetic in healthy mice to establish its metabolism and distribution. Quantitative analysis of antimony from liposomes demonstrated that Neutron Activation Analysis was the most sensitive technique with almost 100 % of accuracy. All liposome formulations presented a mean diameter size of 150 nm. The determination of IC50 in infected macrophage showed that liposome formulations were between 10 63 fold more effective than the free drug, indicating higher selectivity index. By fluorescence microscopy, an increased uptake of fluorescent-liposomes was seen in infected macrophages during short times of incubation compared with non-infected macrophages. Biodistribution studies showed that meglumine antimoniate irradiated encapsulated in liposomes of phosphatidylserine promoted a targeting of antimony for MPS tissues and maintained high doses in organs for a prolonged period. In conclusion, these data suggest that meglumine antimoniate encapsulated in liposomes showed higher effectiveness than the non-liposomal drug against Leishmania infection. The development of liposome formulations should be a new alternative for the chemotherapy of infection diseases, especially Leishmaniasis, as they are used to sustain and target pharmaceuticals to the local of infection.

Orientador: José Anchieta Gomes Neto / Banca: Edilene Cristina Ferreira / Banca: Marcia Andréia Mesquita Silva da Veiga / Resumo: Foram desenvolvidos métodos de determinação de Sb e Pb por espectrometria de absorção atômica com fonte contínua e alta resolução empregando amostragem direta de sólidos. A determinação direta de Sb e Pb foi possível com calibração em meio aquoso utilizando 5 μg de Pd e 2,5 μg de Mg em presença de 0,05% (m/v) de Triton-X como modificador químico. Para o Sb, as temperaturas de pirólise e de atomização foram 1600 °C e 2200 °C respectivamente. O método apresentou massa característica de 1,0 ng e limite de detecção de 0,6 ng. Para o Pb, as temperaturas de pirólise e de atomização foram 1400 °C e 2000 °C respectivamente. A massa característica foi de 5,2 pg e o limite de detecção 4,9 pg. Os desvios padrões relativos do Sb e Pb foram de 2,8% e 4% respectivamente. Estudos de homogeneidade e massa mínima sugeriram boa precisão e exatidão dos métodos na determinação de Sb e Pb em embalagens PET, quando massas entre 0,3 e 0,4 mg para Sb e 0,5 a 0,8 mg para Pb foram utilizadas. Quatro amostras de embalagens PET de diferentes cores foram analisadas pelo método proposto, as concentrações variaram 176,7 a 250,1 mg kg-1 para Sb e de 26,5 a 81,7 pg mg-1 para Pb. Os resultados comparativos obtidos para Sb e Pb empregando HR-CS FAAS e ICP-MS respectivamente, foram concordantes ao nível de 95% de confiança, exceto para o Sb na amostra de PET incolor. O método mostrou-se viável para quantificação dos analitos propostos podendo ser utilizado para controle de qualidade dos PETs, especialmente os que armazenam produtos alimentares. / Abstract: Methods development were proposed for the determination of Sb and Pb in polyethylene terephthalate (PET) package by high-resolution continuum source atomic absorption spectrometry using direct solid sampling approach. Direct analysis using aqueous standards calibration was possible by using a proper heating program of atomizer and 5 μg Pd and 2.5 μg Mg as modifier in presence of 0.05% (m/v) Triton X-100. With regards to Sb, the pyrolysis and atomization temperatures were 1600°C and 2200°C, respectively. Calibration curves in the 0 - 100 ng range with linear correlation coefficient better than 0.9997 were obtained. The characteristic mass and limit of detection (LOD) were 1.0 ng Sb and 0.6 ng Sb, respectively. The relative standard deviation was 2.8%. For Pb, the of pyrolysis and atomization temperatures were 1400°C and 2000°C, respectively. Calibration in the 0 - 160 pg working range was obtained (R=0.9998) and the relative standard deviations were  4%. The characteristic mass was 5.2 pg Pb and the LOD was 4.9 pg Pb. Studies on homogeneity and minimal mass showed that acceptable precision and accuracy for Sb and Pb may be acquired if masses in the 0.3 - 0.4 mg and 0.5 - 0.8 mg were respectively weighted. PET samples at different colors were analyzed by the proposed method based on direct soid sampling. The concentrations varied from 176.7 to 250.1 mg kg-1 Sb and 26.5 to 80.9 pg mg-1 Pb. These results were in agrement with those obtained by high-resolution continuum source flame atomic absorption spectrometry (for Sb) and inductively coupled plasma mass spectrometry (for Pb) at 95% confidence level (except for the colorless PET). / Mestre

Since the UK industrial revolution, coal combustion, ore smelting and other industrial activities have resulted in a marked increase in emissions of potentially toxic elements (PTEs) such as antimony (Sb), lead (Pb), arsenic (As), copper (Cu) and zinc (Zn), along with polycyclic aromatic hydrocarbons (PAHs), to the atmosphere. Although stricter environmental regulation and improved technology has led to a notable decline for some contaminant emissions in recent decades, this has not been observed for all elements, e.g. Sb, where only a modest reduction in emissions have been recorded. Once emitted, Sb along with Pb, As, Cu, Zn and PAHs may persist in the environment for considerable periods of time after their release; although their chemical associations may change, elements are not broken down over time and organic contaminants may break down slowly. Above all, PTEs and PAHs are detrimental to human and environmental health, with chemical forms of Sb, Pb, As and PAHs categorised as carcinogenic. Understanding their behaviour and fate in the environment is therefore an important step towards evaluating their likely impact on both ecosystem and human health. Consequently, this study focuses on the release, behaviour and fate of contaminants from current and past anthropogenic sources in the urban and rural environment, with a specific interest in Sb and PAHs, where emissions originate from similar anthropogenic sources, with Pb, As, Cu and Zn also included for comparison purposes. Current and past industrial activity was identified as the dominant source of PTEs and PAHs to the urban environment, with emissions from vehicle, coal combustion and metal smelting identified as main contributors to total contaminant concentrations. Using road dust collected from Edinburgh at five high- and low-traffic roads at a distance of 10 and 50 m from the closest road junction, concentrations of Sb, Pb, Cu, Zn, PAHs and Pb isotope ratios were determined, with road dust undergoing further characterisation using chemical (sequential extraction) and spectroscopic (X-ray diffraction, SEM-EDX) techniques. No consistent trend for the element concentrations released from vehicles braking at 10 and 50 m from the closest road junction was observed. Mean concentrations for Sb, Cu and Zn were 5.3 ± 2.8 mg kg-1, 91.4 ± 48 mg kg-1 and 237 ± 144 mg kg-1, respectively, and were similar to road dust sampled from five high- and five low-traffic locations in Glasgow (Sb 4.5 ± 2.1 mg kg-1; Cu 117 ± 71.9 mg kg-1; Zn: 283 ± 146 mg kg-1). This was in contrast to mean concentrations for Pb and Σ16PAHs obtained from Glasgow (Pb 250 ± 283 mg kg-1, Σ16PAH 7.7 ± 4.3 mg kg-1) where values were approximately double and two-thirds greater than those found in Edinburgh (Pb 135 ± 129 mg kg-1, Σ16PAH 4.7 ± 2.9 mg kg-1), respectively. Lead isotopic analysis of Glasgow road dust (206Pb/207Pb range of 1.140-1.174) showed a strong influence of past emissions from coal combustion and metal smelting, and was in agreement with Glasgow's industrial history. For Edinburgh, the isotopic signature was considerably lower (206Pb/207Pb range of 1.116-1.151), and was influenced moreso by emissions of Australian sourced Pb in leaded fuel. Isotopic signatures in Edinburgh were lowest at easterly locations within 5 km of Edinburgh airport (206Pb/207Pb ~ 1.12), and corresponded with past vehicle emissions from leaded petrol use, and to a lesser degree, emissions from avgas, which was consistent with the mean annual wind direction for Edinburgh. The mobility of elements from the road dust to the aqueous phase were assessed by sequential extraction, and by using road surface water samples which showed mobility decreased in the order of Zn > Cu > Pb > Sb. Road dust characterised by XRD and SEM-EDX had a high proportion of quartz present (~55%), whilst the presence of less abundant minerals such as calcite were found to increase Pb mobility through ease of dissolution into the aqueous phase. For the rural environment, the behaviour and fate of elemental pollution originating from two former mining sites, an Sb mine at Glendinning, SW Scotland, and a Pb mine at Tyndrum in central Scotland was examined. Under specific environmental conditions, Sb was found to be both mobile and immobile in the environment. The chemical weathering of stibnite found in spoil heaps at Glendinning Sb mine demonstrated that ~3% of total Sb can be mobilised during the chemical weathering process, while hydrous Fe oxides and organic matter in the surrounding soil favoured its retention. The retention of Sb, along with Pb, was similarly observed in Loch Tay sediment downstream of Tyndrum Pb mine, where upon deposition, Sb and Pb remained immobile in sediment and allowed the construction of deposition chronologies for two sediment cores to be established. Excellent agreement between the sediment core deposition chronologies was observed, with both chronologies identifying atmospheric deposition as the primary source of Sb to Loch Tay sediment, whilst the dominant source of Pb was from Tyndrum Pb mine ~25 km upstream of Loch Tay. Relative to Sb and Pb, As had the greatest mobility, with its geochemical behaviour and partial retention by the solid phase influenced by the presence of Fe. This was evident in the surrounding soil at Glendinning Sb mine, where As was associated with hydrous Fe oxides present in the solid phase, while at Loch Tay, the redox cycling of Fe resulted in the post-depositional mobility of As in sediment. The use of ombrotrophic peat bogs for this study provided an effective means to assess atmospheric deposition of contaminants over past centuries; they continually accumulate and receive all their nutrients and contaminants exclusively by deposition from the atmosphere. The deposition archives of Sb and Pb from two Scottish peat cores sampled from Great Moss, Cairngorms Mountains, and, Auchencorth Moss, Midlothian, were used to construct chronologies for historic and contemporary emissions, particularly in relation to current and historic anthropogenic activities observed in urban and rural environments. At Great Moss, the deposition of Sb and Pb during the 19th century increased by a factor of 10 and 4, respectively, as a result of the industrial revolution and emissions from the combustion of coal and metal smelting. The trend continued into the 20th century where Sb and Pb deposition peaked ~1950, followed by a decline towards the early 21st century by a factor of 5 and 11, respectively. Over this period of time, the contribution from coal combustion and metal smelting towards total anthropogenic emissions was on the decline, while emissions from the combustion of leaded fuel increased until the ~1980s. Although deposition chronologies before 1970 for Sb and Pb at Auchencorth Moss were generally in agreement with those from Great Moss, several differences were observed after 1970, or more specifically, in the top ~10 cm of the peat core. This was a result of sub-surface perturbations for Ti, Sb, Pb and 210Pb concentrations, and indicated once deposited, elements were susceptible to post-depositional mobility brought about from a change in environmental conditions. The thicker acrotelm layer present at Auchencorth Moss, and the vertical movement of the peat water-table within this layer, resulted in a change in redox conditions and led to the redox cycling of Mn and Fe, which in turn, influenced vertical concentrations of Ti, Sb, Pb and 210Pb. While Sb and Pb are usually found immobile in peat systems, the post-deposition mobility of Sb and Pb at Auchencorth Moss was comparable to a peat core sampled from Flanders Moss, and indicated that under specific environmental conditions, both elements can become mobile in ombrotrophic peat bogs. It is worth bearing in mind however, that these results are the exception, and in all other cases ombrotrophic peat bogs remain a reliable archival material to use.

Leishmanioses são um complexo de doenças infecciosas causadas por protozoários intramacrofágicos do gênero Leishmania, fatal se não tratadas adequadamente. Os antimoniais pentavalentes são os medicamentos de primeira escolha para o tratamento, apesar de sua toxicidade e seu mecanismo de ação pouco esclarecido. Uma terapia mais eficaz pode ser conseguida pelo direcionamento de fármacos antileishmania para os locais de infecção. Os lipossomas são vesículas lipídicas que promovem melhora na eficácia e na ação de fármacos na célula alvo. Os lipossomas são capturados preferencialmente pelas células do sistema mononuclear fagocitário (SMF). O objetivo deste estudo foi desenvolver uma formulação de antimoniato de meglumina lipossomal, constituído por fosfatidilserina e estudar sua farmacocinética em animais sadios para esclarecer seu metabolismo e distribuição. As análises quantitativas de antimônio em lipossomas demonstram que Análise por Ativação Neutrônica foi a técnica mais sensível com cerca de 100 % de precisão. Todas as formulações de lipossomas apresentaram um tamanho de diâmetro médio de 150 nm. A determinação da CE50 em macrófagos infectados mostrou que as formulações de antimoniato de meglumina encapsulado em lipossomas foram entre 10 - 63 vezes mais eficazes do que a fármaco livre, indicando maior índice de seletividade. Por microscopia de fluorescência, foi verificada uma maior internalização de lipossomas fluorescentes em macrófagos infectados durante um curto tempo de incubação em comparação com macrófagos não infectados. A biodistribuição do antimoniato de meglumina irradiado encapsulado em lipossomas contendo fosfatidilserina mostrou que a formulação lipossomal promoveu um direcionamento seletivo do antimônio para tecidos do SMF, além do que manteve as doses elevadas nos órgãos por um período prolongado. Em conclusão, estes dados sugerem que o antimoniato de meglumina encapsulado em lipossomas apresentou maior eficácia do que a fármaco não lipossomal contra a infecção por Leishmania. O desenvolvimento de formulações lipossomais pode ser uma nova alternativa para a quimioterapia de doenças infecciosas, especialmente Leishmanioses, já que são usados como sistemas carreadores para entrega sustentada e direcionada de fármacos ao local da infecção. / Leishmaniases are a complex of parasitic diseases caused by intramacrophage protozoa of the genus Leishmania, and is fatal if left untreated. Pentavalent antimonials, though toxic and their mechanism of action being unclear, remain the first-line drugs for treatment. Effective therapy could be achieved by delivering antileishmanial drugs to these sites of infection. Liposomes are phospholipid vesicles that promote improvement in the efficacy and action of drugs in target cell. Liposomes are taken up by the cells of mononuclear phagocytic system (MPS). The purpose of this study was to develop a preparation of meglumine antimoniate encapsulated in liposomes of phosphatidylserine and to study its pharmacokinetic in healthy mice to establish its metabolism and distribution. Quantitative analysis of antimony from liposomes demonstrated that Neutron Activation Analysis was the most sensitive technique with almost 100 % of accuracy. All liposome formulations presented a mean diameter size of 150 nm. The determination of IC50 in infected macrophage showed that liposome formulations were between 10 63 fold more effective than the free drug, indicating higher selectivity index. By fluorescence microscopy, an increased uptake of fluorescent-liposomes was seen in infected macrophages during short times of incubation compared with non-infected macrophages. Biodistribution studies showed that meglumine antimoniate irradiated encapsulated in liposomes of phosphatidylserine promoted a targeting of antimony for MPS tissues and maintained high doses in organs for a prolonged period. In conclusion, these data suggest that meglumine antimoniate encapsulated in liposomes showed higher effectiveness than the non-liposomal drug against Leishmania infection. The development of liposome formulations should be a new alternative for the chemotherapy of infection diseases, especially Leishmaniasis, as they are used to sustain and target pharmaceuticals to the local of infection.

Ph. D. thesis, University of Hong Kong, 1979.

The fluoride anion plays an important role in dental health and as a result is added to drinking water at low concentrations. If the concentration of fluoride is too high however, skeletal fluorosis can occur. Because of this, there has been significant interest in the development of water compatible anion sensors that can sense fluoride at the ppm level. This is made difficult by the high hydration enthalpy of fluoride (ΔH0 = -504 KJ/mol) which significantly lowers the reactivity of this anion in water. For this reason it has become the goal of the Gabbaï group, as well as other research groups to develop fluoride sensing small molecules. Such molecules should possess sufficient Lewis acidity to overcome the hydration enthalpy of the fluoride anion. A significant amount of research has been conducted on triarylboranes containing cationic moieties such as ammonium, phosphonium, and sulfonium groups. This thesis will describe additional examples of such species, including a series of ammonium boranes of the general formula [p-(Mes2B)C6H4(NMe2R)]+. As indicated by anion complexation studies, the R group present in these molecules has a notable effect on the anion affinity of the somewhat distant boron center. Another component of this thesis deals with the chemistry of newly synthesized stiboranes that are also decorated by peripheral ammonium groups. As observed for the ammonium boranes mentioned above, the ammonium groups present in these stiboranes drives anion capture, leading to zwitterionic ammonium antimonite formation.